JSON视图中的分层树

Question

I need to develope a webservice in hierarchical tree structure. I have tried a lot but Iam not getting the expected result. i have given my DB, code below and also my expected result.. Please help me

this is my db

category_id     parent_id
1
2               1
3               1
4               2
5               2
6               4   
7               5
8               3
9               3
10              6

Here is my code

<?php
error_reporting(E_ALL ^ E_DEPRECATED);
error_reporting(0);
mysql_connect("localhost","root","");
mysql_select_db("hierarchical");
function display_children($parent, $level) { 
$result = mysql_query('SELECT `category_id` FROM `category` WHERE `parent_id`="'.$parent.'";'); 
while ($row = mysql_fetch_array($result)) { 
//echo str_repeat('  ',$level).$row['category_id']."n"; 
$res[]=array("Categoty"=>$row['category_id']);
display_children($row['category_id'], $level+1); 
}
$response = array("Success" => "1", "Details" => $res);
$final = array("response" => $response);
echo json_encode($final); 
} 
echo display_children(1, 1);
?>

My expected result is

    {
    response: {
    Success: "1",
    Details: [
            {
            Categoty: "2"[
                {
                    Categoty: "4"[
                    {
                        Categoty: "6"[
                        {
                            Categoty: "10"
                        }
                        ]
                    }
                    ]
                    Categoty: "5"[
                    {
                        Categoty: "7"
                    }
                    ]
                }

                ]
            },
            {
            Categoty: "3"[
                {
                    Categoty: "8"
                }
                {
                    Categoty: "9"
                }
                ]
            }
        ]
    }
}